System for eliminating static



May 7, 1935. c. N. LOEWENSTEIN' 2,000,142

SYSTEM FOR ELIMINATING STATIC I I Filed June s, 1935 *UNITED STATES PATENT OFFICE SYSTEM FOR ELIMINATING STATIC Casper N. Loewenstein, Columbus, Ohio Application June 8, 1933, Serial No. 674,359

30laims.

This invention relates to an improved method of and means for eliminating static disturbances from a radio receiving system so that the reception of incoming signals will be substantially free from undesired interference, thus providing a more eificient system for the reception and audible reproduction of the signals.

An object of the invention is to provide an improved system for the elimination of static disturbances from a radio receiving system in which one circuit receives the radio signals with static disturbance and another circuit receives the static disturbance without the radio signals, and by heterodyning one of the circuits until it is of the same frequency as the other, thereby balancing out the static disturbances from the two circuits, and per mitting the reception of the radio signals free from this interference. Another object of the invention is to provide an improved system for the elimination of static disturbances from a radio receiving system in which one circuit receives the radio signals with static disturbance and another circuit receives the static disturbance without the radio signals, and wherein provision is made of a separate oscillator for each circuit.

extending through a grid leak 8 and a grid condenser 9. A variable condenser I is shunted across the secondary windings of the transformer 6'], as shown. Also, the secondary 5 is connected to the filament of the tube 1 through the secondary H of a transformer l2. The plate 26 of the tube 1 is connected to the B power supply preferably through a radio frequency choke coil 22a and the side A of the split primary 23 of a transformer 24, there being a balancing control as indicated at 25. The radio frequency current through both sides of the split primary 23 of the transformer 24 is returned to the filaments of their respective tubes through the provision of by-pass condensers 63 and 64 which are connected from the. centerof the split primary 23 of the transformer 24 to the filaments l3 and 41 of the tubes 1 and 35 respectively; The filament I3 is connected to the A power supply through the radio frequency choke coils indicated at 22b and 220. The primary l9 and 60 of the transformer l2 constitutes in effect a grid circuit and a plate circuit. The grid coil is .:connected to the filament 5| of the tube I5, while the other side of the grid coil is connected to the grid I 4 of said tube l5 through the grid condenser A further object of the invention is to providey l1 and grid leak I6. A variable condenser I8 is an improved system for the elimination of static shunted across the grid coil IQ of the transformer disturbances from a radio receiving system in l2. The plate 20 of the tube l 5 is connected to the 5 which one circuit receives .the radio signals with i 13 power supply through the radio frequency choke. tatic disturbance and another circuit receives the i coil 22d and to the plate coil 60- through the bytatic disturbance without the radio signals, and i pass condenser 2|. The other side of the plate n which one circuit may be straight radio freizcoil 00 is connected to the filament 5| of the tube quency amplification and the other circuit tuned while the secondary 30 of the transformer 62 5' to a higher frequency and heterodyned. is connected to the grid 34 of the tube 35 through 35 i Other objects will appear as the description proceeds.

In the accompanying drawing which forms a part of my application:

Fig. 1 is a diagrammatic view of my improved system for eliminating static disturbances from a radio receiving system;

Fig. 2 is a diagrammatic view of a modified system for eliminating static disturbances from a radio receiving system, in which the signals are not heterodyned.

Referring more particularly to the drawing and the-form of the invention diagrammatically illustrated in Fig. 1, an antenna I is shown as connected to the primary windings 2 of a transformer GI and also, the primary windings 3 of a second transformer 62 and thence to a suitable ground indicated at 4. The secondary winding 5 of the transformer Si is connected to the grid 6 of an ordinary radio tube 1, the said connection the grid leak 32 and grid condenser 33. The other side of the secondary 30 of the transformer 62 is connected to the filament 41 of the tube 35 through the secondary 45 of a transformer 46. The plate 35 of the tube 35 is connected to the B power supply through the radio frequency choke coil 22a, and the side B of the split primary 23 of the transformer 24. The radio frequency current delivered to both sides of the split primary 23 is by-passed to the filaments of the responding tubes through condensers 63 and 64. v

The balancing control indicated at 31 is connected between the plate 35 of the tube 35 and the side B of the secondary 23 of, the split primary transformer 24; The primary 55 and 66 of the transformer 45 functions as a grid circuit and plate circuit. The grid coil is connected, to the filament 52 of the tube 44, while the other side of the grid coil is connected to the grid 43 of the tube 44 through the grid leak 4| and grid condenser 42. A variable condenser 40 is shunted across the grid coil 65 of the transformer 46, while the plate 49 of the tube 44 is connected to the B power supply through the radio frequency choke coil 220. The plate coil 66 of the transformer 46 is connected to the plate 49 of the tube indicated at 44 through the by-pass condenser 50.

In the operation of the hereinbefore described system, either of t l e g. ntenna circuits agetuned to the frequency of thefignaifwith static, and the other circuit is tuned to a frequency as close as possible which has no signal. Then the oscillator using transformer I2 and tube I5, and the oscillator using transformer 46 and tube 44 are each tuned so that they both produce the same beat frequency in the respective grid circuits of the circuits using the secondary inductance 5 and tube I, and the secondary inductance 30 and tube 35, with the impulses received from the antenna. Thus in the plate circuits of the tubes 1 and 35, there will be equal beat frequencies which are in opposition in the split primary 23 of the transformer 24, when there are static impulses. Due to the fact that both signals are originally tuned to nearly the same frequency, the same static impulse will be in both halves of the split primary 23 at the same time, but the signal impulse will he on one side only, and there will be no signal impulse in opposition, as in the case of the static impulses. This condition will eliminate static impulses in the secondary 21 of the transformer 24 which is tuned to the beat frequency, and leave only the signal impulse. The control of the balance is obtained through the variable resistors 25 and 31, because they vary the plate voltages for tubes 7 and 35.

In the diagrammatic illustration shown in Fig. 2, I do not employ a heterodyne circuit, but rather provide a straight radio frequency circuit for receiving the signals with static, and a detector circuit for receiving the static at the nearest frequency to that of the first circuit but with no signal. The second circuit is used with an audio frequency transformer which is used .to modulate the oscillator circuit, which in turn is tuned to the same frequency as the first and second circuits. There is a split primary of the radio frequency transformer on one side of which there are signals with static, and on the other side static but no signals, and the frequency, Dowerand amplitude will be the same on the opposite sides of the primary, but the static will be opposed in the two sides and will consequently balance out the static so that only the signals will pass to the secondary, and from thence to the detector or radio frequency amplification of the receiving set. It is intended that all circuits in both Figs. 1 and 2 will be properly shielded, to avoid the picking up of static impulses after the balancing out has been effected.

In the form of the invention disclosed in Fig. 2, the antenna 60a is connected to the primary Gla of transformer I00. The other side of the primary 6| a is connected to the primary 62a. of a transformer IIII and, likewise, the other side of the primary 62a is connected to the ground 63a. The secondary 64a of the transformer I00 is connected to the grid 66a of a radio tube 61a, while the other side of the secondary 64a is connected to the filament 68 of the tube 61a. A variable condenser 65a is shunted across the transformer secondary 64a.

The plate 69 of the tube 61a. is connected to the side X of the primary I0 of a split primary radio frequency transformer II, this being accomplished through the condenser 14 and the variable resistance indicated at I2. The center of the primary III of the transformer 1| is connected to the B power supply through the radio frequency choke coil I02. A by-pass condenser I03 is connected from the center tap of the primary I0 of the transformer II to the filament 68 of the tube 61a. A condenser I04 is shunted across the secondary I3 of the transformer II. The circuit using the secondary 13 is adapted to be tuned to the same frequency as the circuit using the secondary 64a of the transformer I00, condenser 85a and tube 61a.

One side of the secondary I5 of the transformer MI is connected to the grid 11 -'of a radio tube I8 through the grid condenser and the grid leak I9. A variable condenser I6 is shunted across thesecondary 15 of the transformer IN. The other side of the secondary I5 of the transformer IOI is connected to the filament 8| of the tube I8. The plate 82 of the tube 78 is connected to the B power supply through the primary 83 of an audio frequency transformer III). One side of the radio frequency by-pass condenser I01 is connected to the filament 8| of the tube 18. The other side of the radio frequency by-pass condenser I0! is connected to the plate side of the primary of the audio frequency transformer 83. One side of the grid coil 85 of the oscillation transformer 86 is connected to the grid of the tube 88. Also one side of the grid leak H2 is connected to the filament 89 of the tube 88, while the other side of the grid leak I I2 is connected to the grid 90 of the tube 88.

The plate coil I I3 of the transformer 86 is connected to the filament 89 of the tube 88, while the other side of the plate coil II3 of transformer 86 is connected to the plate 81 of the tube 88 throulgh the radio frequency by-pass condenser II The plate 8'! of the tube 88 is connected to the B power supply through the radio frequency choke coil I09, the secondary 84 of the audio frequency transformer H0, and radio frequency choke coil I02. In this instance, the audio frequency transformer H0 acts as an amplifying transformer and also as a modulating transformer. The condenser shown at I I4 is connected across the grid coil 85 of the transformer 86 and is used to tune the oscillation circuit to the same frequency as the incoming frequency in the secondary 64a of the transformer I00. One side of the secondary 9| of the transformer 86 is connected to the filament of the tube 94. The other side of the secondary 9| of the transformer 86 is connected to the grid 93 of the tube 94. A condenser 92 is shunted across the secondary 9| of the transformer 86. The variable condenser 92 is used to tune the secondary 9| of the transformer 86 to the same frequency as the frequency of the oscillator. The plate 96 of the tube 94 is connected to the side Y of the split primary I0 of the transformer 1|, by way of the condenser I05 and the variable resistance 91. The center tap of the split primary I0 of the transformer 'II is the point B power supply for the tubes 94 and 610.. One side of the radio frequency by-pass condenser I06 is connected to the center of the split primary I0 of the transformer II, while the other side of the condenser I06 is connected to the filament 95 of the tube 94. Radio frequency by-pass condenser I03 is used to complete the plate radio frequency circuit of tube 61a, in the same manner that radio frequency by-pass condenser I06 is used to complete the radio frequency plate circuit of tube 94.

The two radio frequency choke coils 98 and 98 also serve to separate circuits as much as possible. The usual A supply is connected to the filaments of the several tubes, and the B supply is connected as shown, with the proper use of the choke coils 98, to avoid the'picking up of static impulses other than in the antenna circuits.

All parts of the entire system must be properly shielded.

From the foregoing description, taken in conjunction with the two diagrammatic circuits, it will be apparent that I have provided two hookups which will positively and effectively eliminate static from the incoming signals received by a radio receiving set, the first and preferred hook-up utilizing heterodyning, and the second hook-up utilizing straight radio frequency, with audio frequency being used to modulate an oscillator which re-transmits to the receiver. Both circuits excite a single amplifier or detector circuit with the use of a split primary radio frequency transformer. In the first hook-up, I have used two oscillators, which is believed to be a decided advance over the patented art as this' particular system of heterodyning will not produce useless, harmful, and annoying oscillations from being picked up in any but their intended circuits. This also prevents any radiations from being transmitted from the receiver to any other 7 place.

-Minor changes in connections and arrangement may be made without departure from the spirit of the invention.

What is claimed is:-

1. A radigl gk-up for the elimination of static including two detector circuits each having a detector tursaafia'sraarc frequency transformer having a split primary, the sides of which are connected respectively with the plate elements "in the said detector tubes, one detector circuit being tuned to receive a desired signal with static andtliebthefdetector circuit beingt ed to as close a frequency as possible to that of t e first circuit but with static and no signal, vacuum tube oscillators for each detector circuit for producing the same beat frequency in the grid circuits of the detector circuits, whereby the beat frequencies from the plate circuits of the detector tubeswill be equal but opposed in the opposite sides of the said split primary of the radio frequency transformer.

2. A radio hook-up as set forth in clainrl, and separate means connected with each side of the split primary of the radio frequency transformer for varying the amplitude of the static impulses.-

3. A radio hook-up as set forth in claim I havi ngasinglg ai tenna for receiving said signals and includinLmeanfsnnseiis for impressing said signals on said detector circuits.

CASPER N. IDEWENS'I'EIN. 

